gistfile1.txt

Some = λx λs λn (s x)
None =    λs λn n

Tie = λval λlft λrgt λtie λnew (tie val lft rgt)
New =                λtie λnew new

BitO = λx λo λi λe (o x)
BitI = λx λo λi λe (i x)
BitE =    λo λi λe e

Got = λmap (map GotT GotN)
  GotT =
    λval λlft λrgt λkey (key
      λpred (GotL val (Got lft pred) rgt)
      λpred (GotR val lft (Got rgt pred))
      ((Tie val lft rgt), val)
    )
  GotN = λkey (New, None)

GotL = λval λlft λrgt
  let (lft, res) = lft
  ((Tie val lft rgt), res)

GotR = λval λlft λrgt
  let (rgt, res) = rgt
  ((Tie val lft rgt) res)

main =
  let map = (Tie (Some 1) New New)
  let key = BitE
  (Got map key)